Longitudinal Assessment of Denervated Muscles in Parsonage-Turner Syndrome with Quantitative MRI

Motivation: Parsonage-Turner syndrome (PTS) is a spontaneous peripheral neuropathy affecting upper extremity nerves and leading to severe muscle denervation. Quantitative MRI (qMRI) can objectively evaluate the degree of denervation and muscle recovery from PTS over time. Goal(s): To characterize PTS-related muscle denervation using qMRI biomarkers and to assess longitudinal changes. Approach: In 21 PTS subjects at up to four timepoints, the associations of T2, apartment fiber diameter (AFD), fat fraction (FF), and muscle volume with electromyography and muscle function were analyzed. Results: Associations between qMRI biomarkers reflect severity of muscle denervation in PTS. Recovery, involving reduced edema and increased atrophy, may follow non-linear patterns. Impact: Quantitative MRI biomarkers including T2 mapping, apparent fiber diameter, fat fraction, and muscle volumetry correlate with electrodiagnostic and functional assessments of denervation and muscle function impairment in Parsonage-Turner syndrome (PTS), and they can longitudinally characterize PTS-related changes.